As a method for manufacturing the color filter, a photolithography has been widely used for a long time. The photolithography is a method including: coating and drying a coloring photosensitive composition on a support to form a colored layer, then exposing and developing the colored layer to form a colored pixel of a first tint (for example, green), and forming a colored pixel of the remaining colors in the same manner.
However, as the pixels of a solid-state imaging device are micronized, it has become difficult to achieve both spectral characteristics and pattern formability of a color filter for the demand for micronization and thinning of the color filter in the pattern formation by a so-called photolithography. Specifically, in a color filter for a solid-state imaging device, the thickness thereof tends to become, for example, 1 μm or less for the thinning of a colored pattern and to become 2 μm or less (for example, 0.5 μm to 2.0 μm) for the pixel pattern size, thereby achieving a microsize.
In particular, as the thinning of a film progresses, the relative amount of colorants such as pigments in a film increases, while the amount of components other than the colorants, which contribute to the photolithographic properties, in a film relatively decreases, and the pattern formability due to the decrease has effects of improving the shape of a pattern observed on the top surface thereof even when a correction such as OPC is performed for the requirement of forming a pattern below 2.0 μm, but there is a problem such as insufficient rectangularity that the pattern edge of the pattern shape is round when observed the cross-section. It is known that in a color filter (a color filter manufactured by photolithography using a coloring radiation sensitive composition in which a pigment is dispersed in various compositions) using a pigment dispersion liquid, the rounding of the pattern edge become significant by influence of light scattering by the pigment when exposuring.
In particular, recently, due to the demand for the higher definition of the color filter for a solid-state imaging device, the formability of a pattern of, for example, 1.4 μm becomes problematic, and thus, the resolution may almost reach a limit in the photolithography in the related art.
For a method for manufacturing a color filter using the photolithography, a processing method using dry etching has been suggested as a method effective to realize micronization and thinning of a pattern. The dry etching has been adopted in the related art as a method for forming a pattern (each colored pixel) in a rectangular form, and a method for forming a pattern which combines the photolithography and the dry etching have been suggested (see, for example, Patent Documents Japanese Patent Application Laid-Open No. 2006-222290 and Japanese Patent Application Laid-Open No. 2007-48774).
However, for the purpose of further enhancing the performance of the solid-state imaging device, it has been still required to suppress a crosstalk (color mixing of light). As a method to solve this, a technique for further thinning the thickness of colored pixels is contemplated. However, in this case, a simple thinning process causes a problem that color formation is insufficient. Therefore, as a technique to solve this problem, it is contemplated to increase the concentration of a colorant in colored pixels. However, on the other hand, it is understood that a problem arises in that dispersion stability is damaged in the liquid of the coloring composition for making colored pixels.
The present invention has been made in consideration of the above-described problems. Therefore, an object of the present invention is to provide a coloring composition having excellent dispersion stability of a colorant in a liquid while containing a high concentration of the colorant in order to further thin colored pixels.
Further, another object of the present invention is to provide a coloring composition capable of reducing the occurrence of overlap region overlapped with colors in other colored layers by forming colored pixels having excellent solvent resistance and alkaline developing solution resistance, and having small change in color in various processes of manufacturing a color filter, thereby making it possible to prepare a color filter having high performance.
Further, still another object of the present invention is to provide a method for preparing a color filter using the coloring composition, a color filter and a solid-state imaging device.